[OZAPRS] Raspbery Pi (RPi) Gateway
vk2tv at exemail.com.au
Mon Sep 3 14:17:37 EST 2012
For somewhere around two years or so I'd been searching for a computer
with low input energy requirements to use as a gateway machine to
replace a conventional desktop system. And then I moved location quite
suddenly which threw my plans into chaos. I'm now in a position to
reestablish gateway facilities with 2m, 30m and satgate facilities, as
per my original gateway.
Although I'd looked at the RPi (http://www.raspberrypi.org/) as a
suitable computer, it was Bernard F6BVP (maintainer of xfbb and fpac)
reporting that he had compiled a kernel with ax25 support that got me
really interested. The latest Debian kernel -
2012-08-16-wheezy-raspbian.img -has kernel ax25 included.
The RPi is a single board computer using a 700MHz ARM processor. It runs
from a single 5V supply. The PCB is about the size of a credit card, has
HDMI and composite video out, audio out, one ethernet port and 2 x USB
ports. They are available from Element 14 (rebadged Farnell) and RS
Components for about $38. See the wiki at
My original intent was to run soundmodem to provide two 1k2 ports but I
found soundmodem unstable and unpredictable on both the RPi and my
desktop environment. In addition, the RPi failed to boot with a Sound
Blaster Play USB dongle plugged in. The dongle is supposed to work OOTB
on the RPi. Other users have reported similar boot problems.
Given that I still have a number of MFJ1270B TNCs I decided that a
hardware approach might be more feasible in the short term. They can
always be replaced by more efficient newer options (TNCX, TT4, etc) in
the fullness of time. In order to run hardware TNCs I needed RS232 ports
so a USB/RS232 adapter was needed. A recommendation from the xastir
mailing list suggested a 4 port FTDI adaptor from DigiKey, at this
The unit cost about $76 with freight and arrived in four days from the
US. I plugged it into the RPi and it worked OOTB. The adapter doesn't
have a case, but neither does the RPi.
Because the gateway system will be away from the house I needed wifi for
Internet access - too difficult to get Cat5 to the shed. I bought a
TP-LINK TL-WN721N USB dongle and it almost worked OOTB. I needed to
install wicd to be able to configure it but it works a treat. In the end
I decided to use my Realtek 8189 equivalent wifi modem for the RPi
because it has an external antenna. It just worked OOTB as well.
The RPi reliably boots with both the USB/RS232 adapter and the wifi
The software I had previously used for the gateway machine is xastir.
It's always done the job and it's stable. The RPi will run headless and
even though I don't "really" need the graphical display of xastir I was
intent on giving it a try. Although there is now a deb package for
xastir (with a current version), I opted to compile xastir on the RPi. I
had already compiled the kernel ax25 surces for libax25, ax25apps and
Although the Raspian distribution is based on Debian Wheezy, not all
packages are available for the ARM processor - yet. This led to some
dependency conflicts that I eventually resolved by seeing what libraries
had been used in the deb package. I finally managed to compile xastir
with all options except festival sound, which I don't need. When I
booted xastir it reported being unable to find libax25.so.1, even though
it exists in /usr/local/lib. For whatever reason, xastir was looking in
/usr/lib so I created a symlink - problem solved.
Xastir is understandably slow when loading raster maps (but lots faster
than xastir 1.4 on a P166 machine some years ago!). For my trial I use
just one map so speed is not an issue. A final installation may have no
map loaded. Xastir is now running as vk2tv-4 but without radio ports at
this stage until I assess reliability. I don't expect any issues.
During my enquiries on the xastir mailing list it was suggested that
xastir is not ideal for a gateway machine (read that previously) and
that I should try aprx which works in a non-graphical environment. I've
also compiled a deb package for the ARM processor and it installed just
fine. aprx has some very flexible configuration options and it reports
lots of statistics on channel usage, etc, as telemetry beacons. It
appears worthy of a trial run s that's my next project.
My goal is to have a solar powered gateway and the RPi has taken me a
lot closer to that goal.
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